On Wednesday night, a 100m section of the road between Kalk Bay and Muizenberg was covered in rocks and mud after part of the mountainside gave way.

The road closure is causing rush-hour delays on alternative routes, especially on the section of Main Road below the contour road. Traffic is being diverted at Clairvaux Road in Kalk Bay and Old Boyes Drive in Muizenberg.

“Luckily there were no injuries or serious damage associated with the rockslide,” said Lakeside councillor David D’Alton. “But Boyes Drive is the main route for most driving commuters from Fish Hoek area. I have personally experienced the toll it has taken on travelling times.”

Disaster Risk Management spokesman Wilfred Solomons-Johannes said a “huge section” of mud and debris had been identified as unstable hours before the road was due to be reopened on Friday. Abseilers were working to dislodge it.

“The potential for further rockslides, and not structural damage and clean-up on the road, is thus the cause for the delay,” he said.

“The road remains closed for the sake of the public’s safety. We are expecting further rains on Wednesday in Cape Town and this may further hamper the infilling and mountainside reinforcement currently under way.”

Mayoral committee member for transport Brett Herron said last night that the city had appointed a geo-technical specialist to determine the extent of remedial work required.

Contour roads on the mountainous ridge of the peninsula are often affected by rock- and mudslides during periods of heavy rainfall.

The city has published a “slope instability” advisory for people who live, work or commute on mountainsides. It shows how to identify the tell-tale signs a landslide is imminent. In buildings on a slope, cracks in the structure or the severance of underground utility lines are warning signs.

The advisory is available on the Disaster Risk Management section of the city’s website.